All of the material in this patent application is subject to copyright protection under the copyright laws of the United States and of other countries. As of the first effective filing date of the present application, this material is protected as unpublished material. However, permission to copy this material is hereby granted to the extent that the copyright owner has no objection to the facsimile reproduction by anyone of the patent documentation or patent disclosure, as it appears in the United States Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.
Not Applicable
1. Field of the Invention
The present invention generally relates to the field of flat panel displays. More particularly to the present invention relates to curing glue seals with radiation that may be partially disposed underneath data/signal lines.
2. Description of the Related Art
In the manufacturing of flat panel displays, it is necessary to bring data and signal lines from within the flat panel structure to a region outside the panel so that the lines can be connected to external driving circuitry. The flat panel typically consists of two substrates, one typically containing the circuitry and another typically containing a color filter, and a liquid crystal material placed in between these substrates. The substrates must be affixed to one another near the periphery of both substrates with a leak tight seal to contain the liquid crystal material. It is in this transition region, between the inside and outside of the panel, that some portions of glue seal used to affix the substrates to one another remain uncured or become only partially cured. In this region, the radiation used to cure the glue seal cannot penetrate the data/signal lines, thus the portions of the glue positioned between the data/signal lines and the second substrate remain uncured. Uncured glue can, overtime, lead to contamination of the liquid crystal material. Therefore, it is important to find ways to insure that the glue seal is thoroughly cured by overcoming the shadowing that prevents radiation from reaching glue seal underneath the data/signal lines.
Uncured glue seal in flat panels has not been a problem in the past because the manufacturing process involved heat sealing of the peripheral regions of the substrates forming the panel prior to their being filled with liquid crystal material. More recently, the xe2x80x98one drop fillxe2x80x99 method, also referred to as ODF, patented by Matsushita (U.S. Pat. No. 5,263,888), where the liquid crystal material is enclosed within between two substrates of the panel prior to curing or polymerizing of the glue seal around the panel periphery, has been used. Sealing of the panel using the ODF method generally requires radiation to be incident on the glue seal to cure or polymerize the glue since the temperature required for conventional oven baking to cure the glue seal would damage the liquid crystal material. The radiation used to cure the glue seal is generally directed onto the substrate whose lower side contains the data/signal lines, thus the lines, impermeable to the incident radiation, prevent the glue disposed underneath them from curing. The radiation cannot be directed from the opposite side of the panel, that is through the lower substrate (which would eliminate shadowing), because that substrate is purposely made opaque in the region of the glue seal and therefore cannot transmit the requisite radiation required for curing or polymerizing the glue seal.
The invention makes use of a thin film pattern disposed on a substrate. The pattern consists of a material that is electrically conducting such that there is electrical continuity between the ends of the pattern, typically a pattern constituting a data/signal line. Additionally, the pattern has a feature that at least one or more local regions of the pattern are interspersed with voids consisting of an absence of electrically conducting material. The conducting material, and the interspersed voids, may occupy an equal amount of surface area. For example, there may be circular or polygonal shaped voids within the conducting material, minimizing the amount of conducting material around the voids while leaving sufficient conducting material to maintain electrical continuity between the ends of the pattern. The size of the voids may vary but will always be less than any linear dimension of the pattern in order to maintain electrical continuity between its ends. While the voids dimension must obviously be greater than zero, in a preferred embodiment each void, and the spacing between voids, may be as small as one micron (1 xcexcm) for a pattern whose line width is on the order of 10xcx9c20 microns, and as large as five microns (5 xcexcm) for a pattern whose line width is on the order of 20xcx9c40 microns. The total area of the missing material or voids may be as much as 90% of the line area and still leave electrical continuity between the ends of the pattern.
In another embodiment, multiple depositions are made. A first layer is disposed that is very thin. The first layer is thin enough to be semi-transparent. Next, a second layer is formed on top of the first layer with a mask. The second layer is formed with a thickness appropriate to the resistance required for electrical continuity. Using this multiple deposition embodiment, the resulting semi-transparent regions form the voids in the thin film pattern.
There may be several voids within close proximity along the pattern""s line width to present a honeycomb structure of voids amidst the electrically conducting material. This kind of structure has particular utility for data/signal lines found in flat panel displays in which the voids in the honeycomb structure are in contact with a glue seal that requires photolytic curing. The voids permit radiation, used for curing, to penetrate through the openings of the honeycomb structure so that most if not all of the glue will be cured by photolytic means without the major area of the lines shadowing the incident radiation used for curing.
In the preferred embodiment as applied to liquid crystal panels, a pattern, consisting of an electrically conducting material with voids, forms a portion of the data/signal lines. The presence of the voids in the pattern allows the radiation, used to cure the glue seal, to reach areas of the glue seal under the data/signal lines that would otherwise be shadowed without the present inventive structure.
Additionally, by varying the angle of incidence of the radiation source with respect to the pattern the irradiated area underneath the data/signal lines around the voids is increased. This method of irradiation, as compared with a fixed angle or perpendicular irradiation, exposes the glue seal in the periphery of the void beneath the pattern to radiation, thus further minimizing the uncured glue spots. Furthermore, for a dual cure glue seal, photolytic and thermally activated glue sealant, the irradiation method further utilizes a multiplicity of radiation frequencies and wavelengths, well known to those skilled in the art, that sets the glue to cure.
The data/signal lines distant from the glue seal region may consist of continuous conducting material, preferably metal, without any voids.
The data/signal lines in the region over the glue seal are patterned using special masks and lithographic techniques to provide the desired local voids. For example, the pattern with voids in the region of the glue seal can be produced using standard lithographic processes. The data/signal lines are fabricated by standard, well known lithographic processes. An additional photoresist step is then applied over the region of the data/signal lines coincident with the glue seal. A mask containing the desired arrangement of voids is positioned over the photoresist covering the data/signal lines. The photoresist is exposed, generally using near UV radiation, and then it is developed. The photolithographic pattern covering the data/signal lines is then exposed to a plasma or chemical etchant, well known to those skilled in the art, to remove the metal defined by the openings in the mask. Finally, the remaining photoresist is removed.